Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 815 · 40 questions

What you do (Heat shows the secret): 1. Dip a cotton bud in lemon juice and write a secret message on white paper. 2. Let the paper dry completely — the writing disappears. 3. An adult irons the paper on a low setting while you watch from a safe distance. 4. Read the brown message and wash your hands.

1. 1.🧺 Which of these is needed for the secret lemon message? (a) yeast (b) a battery cell (c) white paper (d) a magnet
2. 2.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a mirror (c) yeast (d) a cotton bud
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is kept the same. (a) False (b) True
4. 4.🍋 Which of these steps is a job a child can do? (a) writing the message (b) plugging in the iron (c) ironing the paper (d) putting the iron away
5. 5.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it can burn skin (c) it is cold (d) it is sticky
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we change it (b) we measure it (c) we keep it the same
7. 7.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the same paper (b) the same cotton bud (c) how dark the writing is (d) the kind of juice
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we measure it (b) we keep it the same (c) we change it
10. 10.🧺 Do we need a mirror for the secret lemon message? (a) needed (b) not needed
11. 11.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) an adult with an iron (c) a small bowl (d) a battery cell
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we keep it the same (b) we change it (c) we measure it
13. 13.True or false: plugging in the iron is a job a child can do. (a) True (b) False
14. 14.🔍 Which is the odd one out? (a) putting the iron away (b) cutting the lemon (c) writing the message (d) ironing the paper
15. 15.True or false: reading the message is a job a child can do. (a) True (b) False
16. 16.True or false: writing the message is a job for an adult. (a) True (b) False
17. 17.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) almost nothing (c) a rainbow (d) dark brown words
18. 18.🍋 Which of these steps is a job for an adult? (a) ironing the paper (b) reading the message (c) dipping the cotton bud (d) letting the paper dry
19. 19.🔍 Which is the odd one out? (a) ironing the paper (b) writing the message (c) dipping the cotton bud (d) reading the message
20. 20.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
21. 21.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
22. 22.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
23. 23.📘 The browning of lemon juice with heat is a ___ change. (a) musical (b) magnetic (c) physical (d) chemical
24. 24.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) dry juice is see-through (c) the ink is magnetic (d) the paper ate it
25. 25.🔮 Can the brown writing go back to being invisible? (a) yes, if shaken (b) yes, in the dark (c) yes, if cooled (d) no, it stays brown
26. 26.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the ironing time (b) the kind of juice (c) the same cotton bud (d) the iron setting
27. 27.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) writing turns green (c) the paper floats (d) writing stays faint
28. 28.🔍 Which is the odd one out? (a) letting the paper dry (b) reading the message (c) cutting the lemon (d) writing the message
29. 29.True or false: a magnet is needed for the secret lemon message. (a) False (b) True
30. 30.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we keep it the same (b) we change it (c) we measure it
31. 31.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) wash your hands (c) rub your eyes (d) skip washing
32. 32.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) an adult with an iron (c) lemon juice (d) a balloon
33. 33.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
34. 34.🧺 Which of these is not needed for the secret lemon message? (a) a balloon (b) a cotton bud (c) lemon juice (d) an adult with an iron
35. 35.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) blue (c) white (d) brown
36. 36.True or false: a balloon is not needed for the secret lemon message. (a) True (b) False
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) False (b) True
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) False (b) True
39. 39.🍋 Which of these steps is a job for an adult? (a) plugging in the iron (b) writing the message (c) reading the message (d) letting the paper dry
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) how dark the writing is (b) the kind of juice (c) the same paper

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